Short answer: for genuine clinical hydrotherapy, yes, and you should want it that way. The longer answer explains why, and where the exception sits.
Why reputable centres insist on it
A hydrotherapist is working with a body they have not diagnosed. Without the vet's input they do not know whether that limp is a soft tissue strain or a fracture, whether a heart condition makes exertion risky, or whether the dog is on medication that changes what is safe.
Water work on the wrong dog can do real harm. The referral is the mechanism that stops that, and it also means your insurer is far more likely to pay.
What the referral actually is
Usually a short form from your vet confirming the diagnosis, anything the hydrotherapist should avoid, and consent to treat. Most practices handle it routinely. It is not a big process, and it is not designed to be an obstacle.
The exception, stated plainly
No referral is needed to take a healthy dog swimming, because swimming is not treatment. If your dog has no diagnosed condition and you simply want them in water for exercise and enjoyment, a recreational pool is open to you and always has been.
Where we stand on this
Hounds & Waves is a recreational pool, not a clinical hydrotherapy centre. We do not treat conditions and we do not take referrals. If your dog is under veterinary care, follow your vet's advice over anything here.
What to watch out for
Be cautious of anywhere offering clinical-sounding treatment for a diagnosed condition with no referral and no questions. Either they are not doing what they say, or they are doing it without the information they need. Neither is what you want for a dog who is already unwell.
Equally, do not be suspicious of a recreational pool that does not ask for a referral. It should not, as long as it is honest about not being a clinic. There is more on the distinction in our full explanation of hydrotherapy versus swimming.
Recreational swimming in Swindon
No referral, because it is not treatment
A recreational pool for dogs who are well. If yours is not, see your vet first and we will still be here afterwards.
Hydrotherapy or swimming, explained